The Confederates successfully created a working steam-powered machine gun that could fire bullets using centrifugal force.

busted

The MythBusters first tried to confirm whether a steam powered machine gun in fact existed. A Civil War weapons expert confirmed that the weapon actually existed and had the blueprints to prove it. However, the gun’s lethality and effectiveness were unconfirmed. They then constructed a steam gun based on the blueprints they received, with a pair of water heaters providing the steam to spin the barrel. On their test run, they fired a single round which struck the gun’s steel safety shield, creating a deep dent which could potentially cause lethal damage to a person. Satisfied with the test run, the MythBusters took the gun for full scale testing. They tested the gun based on three major factors: a range of 500 yards (460 m), a rate of fire of 400 round per minute, and the fact that the weapon had to be lethal. The gun performed well on the first two criteria, firing five rounds per second at a range of 700 yards (640 m). However, the weapon lacked any lethal force at ranges beyond point blank, and was not very reliable in terms of delivering the bullets to the targets in an effective manner. The MythBusters concluded that as a concept and a machine, the steam gun performed perfectly, but as a weapon, was too unreliable and impractical.

Through mental or physical means, a person can fool a lie detector test from a polygraph machine.

plausible

In order to make the test results genuine, Tory and Grant were instructed to steal money from a safe while the innocent Kari was used as a control. Also, they were promised a reward (first class seats on the next MythBusters trip) for beating the test and a punishment (cleaning and waxing the entire crew’s cars) for failing. During the test, Tory attempted to use pain to hide his lying while Grant tried to focus his mind. However, neither of them could beat the polygraph. While they both failed the test, the Build Team decided not to rule out the possibility that there are people out there capable of fooling a polygraph.

A person can fool a lie detector test from an FMRI, which measures brain activity.

plausible

To set up this test, all three Build Team members had to steal something to fulfill the conditions of the myth. Each member had the choice of stealing either a ring or a watch and then underwent a lie detector test while being scanned by the FMRI. Like before, there was a reward ($1000) and a punishment (a trip back to San Francisco via bus; a 3,077-mile (4,952 km) trip) if they passed or failed the test. Both Tory and Kari tried to think happy and fearful thoughts while Grant tried to keep his brain active for the entire test. In the end, Tory and Kari both failed the test while Grant managed to fool the FMRI, making the myth possible.

A person can repair a fuse box by wrapping a burnt-out fuse with tin foil.

confirmed

Adam took some tin foil from a chewing gum wrapper, wrapped it around a burnt-out fuse, and demonstrated that it could indeed work in a fuse box.